1. Field of the Invention
The present invention relates to a Group III nitride semiconductor light-emitting device and, more particularly, to a Group III nitride semiconductor light-emitting device produced through the laser lift-off technique and providing high-intensity light emission.
2. Background Art
In the growth of Group III nitride semiconductors, a growth substrate made of sapphire is generally employed. Since sapphire is a non-conductive material, flow of current in the vertical direction is impaired. Also, sapphire has low thermal conductivity, which may inhibit radiation of heat generated in a semiconductor device disposed thereon. Difficulty is also encountered in processing of a sapphire substrate, such as dicing, since sapphire has no clear cleavage plane.
The aforementioned laser lift-off technique was developed in order to overcome these drawbacks. In laser lift-off, a Group III nitride semiconductor is grown on a growth substrate, and the interface between the growth substrate and the Group III nitride semiconductor is irradiated with a laser beam, to thereby decompose a part of the Group III nitride semiconductor, whereby the growth substrate is removed from the semiconductor.
Meanwhile, efforts have been made toward the development of techniques for further enhancing light extraction efficiency of such light-emitting devices. For example, Patent Document 1 discloses a GaN-based light emitting device which includes a first uneven structure 160a having a regulated repetition pattern and disposed on the n-GaN layer, and a second uneven structure 160b having an unregulated repetition pattern and disposed on the first uneven structure (see paragraph [0033] and FIG. 3 of Patent Document 1). Such a GaN-based light-emitting device is thought to provide high emission efficiency.    Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2008-47861
Patent Document 1 also discloses that a transparent conductive layer 180 may be formed on the first and second uneven structures 160a, 160b (see paragraph [0039] and FIG. 6 of Patent Document 1). However, the transparent conductive layer 180 may impair the light extraction efficiency from the light extraction face.